On chain polynomials of posets

The chain polynomial of a finite lattice \( \mathcal{L} \) is given by \( p_\mathcal{L} (x) = \sum_{k \geq 0} c_k(\mathcal{L})x^k \), where \( c_k(\mathcal{L}) \) is the number of chains of length \( k \) in \( \mathcal{L} \). The chain polynomials of posets in several important classes have been proven to be real-rooted, for example, face lattices of simplicial and cubical polytopes, and (3+1)-free posets, proved by Brenti and Welker, Athanasiadis, and Stanley, respectively. However, Stembridge presented some distributive lattices that do not have real-rooted polynomials. Recently, Athanasiadis and Kalampogia-Evangelinou conjectured that the chain polynomials of geometric lattices are always real-rooted. We present a sufficient theorem that proves this conjecture for the lattice of flats of paving matroids and generalized paving matroids. We also apply this theorem to other posets to verify that their chain polynomials are also real-rooted. This is a joint work with Petter Brändén. 

Date:  2024-06-26
Start Time:   15:00
Speaker:  Leonardo Saud Maia Leite (KTH Royal Institute of Technology, Sweden)
Institution:  KTH Royal Institute of Technolog, Sweden
Place:  Sala 2.4, DMUC
Research Groups: -Algebra and Combinatorics
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